Patent Document 1 describes a coated optical fiber having a protective coating layer obtained by curing a UV curable resin composition containing a silane coupling agent on the outer periphery of a glass optical fiber. Moreover, Patent Document 2 describes an optical fiber having a primary coating layer and a secondary coating layer and using a silane coupling agent having a mercapto group as a silane coupling agent that is contained in a photo curable resin composition to be used for forming the primary coating layer.